The present invention relates to a method of manufacturing a color cathode ray tube having a superhigh definition, and more particularly to such a method which prevents separation of a fluorescent layer formed on a panel by a so-called external surface exposure process and also prevents undue deposition of a fluorescent substance at an undesired portion on the panel.
To reproduce a highly fine image on a color cathode ray tube, it is necessary to clearly form very fine fluorescent stripes (or dots) of three primary colors on a fluorescent face of the color cathode ray tube without separation.
As a conventional method of manufacturing such a color cathode ray tube, there has been disclosed in Japanese Patent Laid-open Publication No. 60-119055 by the present assignee a so-called external surface exposure process wherein mixing of colors between adjacent stripes is prevented by using two kinds of photosensitive resins different in reversing capability with respect to an aqueous solution of hydrogen peroxide. More specifically, a resist layer employing a first photosensitive resin which can be reversed by an aqueous solution of hydrogen peroxide and a fluorescent slurry containing a second photosensitive resin which cannot be reversed by an aqueous solution of hydrogen peroxide and a fluorescent pigment dispersed in the resin are applied to glass panel on which carbon stripes are preliminarily formed in a predetermined sequence, and are hardened by exposure to form a fluorescent face.
Further, there has been disclosed in Japanese Patent Application No. 62-39806 by the present inventors an improvement of the above-mentioned method, wherein a transparent protective coat of a photo-hardening resin which is not reversed by an aqueous solution of hydrogen peroxide is formed on an entire surface of a glass panel on which carbon stripes are preliminarily formed, so as to prevent separation of the carbon stripes.
As to the photosensitive resin which cannot be reversed by an aqueous solution of hydrogen peroxide as used in the above-mentioned methods, there has been disclosed in Japanese Patent Laid-open Publication No. 55-23163, for example, a photosensitive resin formed by introducing a styryl pyridinium into polyvinyl alcohol or partially saponified polyvinyl acetate. There has been also disclosed in Japanese Patent Laid-open Publication No. 61-230138 a photosensitive resin formed by introducing a styryl quinolinium in addition to the above-mentioned styryl pyridinium into partially saponified polyvinyl acetate. A photochemical reaction of these photosensitive resins is based on an optical cross-linking reaction due to dimerization of the styryl pyridinium or the styryl quinolinium introduced as a side chain.
In the above-mentioned external surface exposure process, a reversal treatment by an aqueous solution of hydrogen peroxide is always carried out every time the fluorescent stripe (or dots) of one color is formed. Accordingly, the fluorescent stripe of a first color formed at the first time is subjected to the aqueous solution of hydrogen peroxide again in the subsequent reversal treatment for forming the other fluorescent stripes of the remaining two different colors.
However, in the case of using the photosensitive resin formed by introducing the styryl pyridinium into polyvinyl alcohol, a resistance of the fluorescent stripes against the aqueous solution of hydrogen peroxide is lacking to cause separation of the fluorescent stripes and chipping of edges of the fluorescent stripes. Furthermore, such embrittled fluorescent stripes tend to be separated when they are washed under an increased water pressure after the reversal treatment by the aqueous solution of hydrogen peroxide.
On the other hand, when a chemical resistance against the aqueous solution of hydrogen peroxide, etc. is intended to be improved, a resolubility to water is reduced to cause a problem such that the fluorescent substance is foggily deposited to an undesired portion on the panel (which will be hereinafter referred to as fogging).